1. Field of the Invention
The present invention relates to a recording apparatus for recording data on a recording tape medium compatible with a so-called timing ATF (Automatic Track Following) servo system as tracking servo control, a recording tape medium on which recording is to be done by this recording apparatus, and a measuring apparatus for measuring a reference value for timing ATF servo in reproducing data from this recording tape medium.
2. Description of the Related Art
Digital data storage equipment (DDS equipment) enabled to record and reproduce computer data has been developed by using a digital audio tape player (DAT recorder/player) for recording and reproducing digital audio data on and from a magnetic tape, for instance, or a DAT system similarly using a magnetic tape, as a data storage system for the computer.
In these apparatuses, high density recording is made possible by causing them to perform recording/reproducing scanning by a helical scanning system using magnetic heads on a rotary drum by having a magnetic tape run in a state wherein the tape is wound round the rotary drum in a lap angle of, for instance, 90xc2x0 and at the same time rotating the rotary drum.
In this case, inclined tracks TKA and TKB, for instance, are formed on the tape as shown in FIG. 20. The inclined tracks TKA and TKB are tracks formed by a pair of heads (head A and head B) mounted on the rotary drum and differing in azimuthal direction, i.e. tracks considered to have inverse azimuths to each other.
Incidentally, whereas the magnetic heads should accurately trace tracks TK on the tape during reproduction, systems to control this tracking include, for example, tracking servo control operation, which is known as timing ATF system, for DDS reproducing apparatuses.
This timing ATF system measures the length of time (tracking detection period) from the reference phase position of the rotary drum until a prescribed signal (timing detection signal) is detected from a track by a head, and the measured value is compared with a reference value, with the error equivalent being used as servo error information.
And, it is caused to be reflected in the tape running speed by controlling the rotating speed of the capstan motor for tape running according to that servo error information. Thus the relative speed with respect to the rotating speed of the drum and the running speed of the tape is adjusted by regulating the running speed of the tape so as to achieve a satisfactory tracking state.
Suppose, for instance as illustrated in FIG. 21, that the phase position of the rotary drum is the reference position when the scanning position of the magnetic head relative to a certain track has come to a positional state corresponding to a line (timing) indicated as TRA in the figure. Since the configuration is such that, at the time when the reference phase position is arrived at during the rotation of the drum, a pulse signal is generated from a pulse generator (PG) arranged on the drum motor, for example, the timing TRA at which the rotary drum has come to the reference phase position can be detected. After that, as the magnetic head comes into contact with the magnetic tape and scans the track TKA, a timing detection signal is detected in a prescribed position PTTP on the track as reproduced data. This timing detection signal is supposed to provide a pulse in the position PTTP predetermined on the basis of a sync signal in the data and the detection of an address.
Whereas three ways of scanning differing in tracking phase state relative to the track TKA are shown here as {circle around (1)}, {circle around (2)} and {circle around (3)} in the figure, the period from the timing of the reference phase position of the rotary drum (the position of the line TRA) until the timing at which the position PTTP is reached (the tracking detection period) varies in length with the way of scanning, {circle around (1)}, {circle around (2)} or {circle around (3)}, as indicated by t1, t2 and t3.
For the tracking detection period, the time length t1, which is obtained when the magnetic head is in a satisfactory tracking state for the track TK, i.e. in a state wherein the center of the track TKA is traced as in {circle around (1)}, is preset and, therefore, if scanning as in {circle around (1)} is performed and the time length t1 is measured as the tracking detection period while under tracking servo control, the measured value and the reference value will coincide with each other. Thus, in this case, there is no error between the measured value and the reference value, and a satisfactory tracking state is found to be achieved. On the other hand, if scanning is performed in a tracking phase state as in {circle around (2)} or {circle around (3)}, the measured value of the tracking detection period will be t2 or t3, and there will be an error compared with the reference value. In this case, there is a tracking lag equivalent to that error, and servo control toward a just tracking state can be executed by causing this to be reflected in the tape running speed.
Whereas the reference value should be identified in advance in executing such timing ATF servo, this reference value, as stated above, is the length of time from the timing of the reference phase position of the rotary drum in the just tracking state until the timing at which a timing detection signal is obtained. As the timing detection signal is generated in accordance with, for instance, the detection of a sync signal at a prescribed address on the track, its position PTTP is fixed on each track of various tapes, but in practice mechanical errors and the like in various recording apparatuses and reproducing apparatuses inevitably give rise to positional lags between a plurality of tracks formed even in a single round of continuous recording. For this reason, when certain file data are to be reproduced with a DDS reproducing apparatus, the reference value on that particular tape (that file data track) should be measured in advance of executing the reading of those data to be reproduced.
For measuring this reference value, such processing is accomplished that scanning of the track is executed in various tracking phase states to calculate an average, for example, from the tracking detection periods measured in those scanning procedures and to use it as the reference value.
Its image is shown, for example, in FIG. 22. If, as illustrated, the track TKA is scanned in a plurality of different tracking phase states, such as TJ1 to TJ5 for instance, and an average is calculated from the different tracking detection periods measured during the scanning procedures, a tracking detection period in the approximate vicinity of the tracking phase state TJ3 in the figure will be obtained. This can be regarded as the tracking detection period substantially in the vicinity of the just tracking state, and accordingly this is used as the reference value.
Incidentally, here is considered a case in which a plurality of recorded areas each formed by one continuous recording operation known as streaming, i.e. execution of a series of actions from the start of recording until the end of recording without stopping the running of the magnetic tape on the way (hereinafter such recording areas may also be referred to as xe2x80x9cstreaming recorded areasxe2x80x9d) are linked to form a recorded area on the magnetic tape.
In this case, in streaming recorded areas each formed by a single round of streaming, the position of the track recorded on the magnetic tape may shift from one streaming recorded area to another, affected by a difference in recording apparatus or, even if recording is performed by the same recording apparatus, by various conditions including mechanical action errors or temperature variations at the time of recording.
Here even if, for instance, a common value is set, as the reference value for the above-mentioned timing ATF servo, by mere scanning for a recorded area formed by linking of a plurality of streaming recorded areas such as described above, this reference value will not necessarily be an appropriate reference value for every streaming recorded area. As a consequence, when tracking is actually executed at the time of reproduction on the basis of a reference value set for timing ATF servo as described above, tracking may not be appropriately executed in some streaming recorded area or areas. Thus, as the reference value for timing ATF servo, an appropriate value for each streaming recorded area should be set.
A method to set a reference value for timing ATF servo suitable for each streaming recorded area conceivably is, for example, to distinguish the section (equivalent to detection of an append point) for each streaming recorded area by detecting a data pattern inherent among streaming recorded areas (e.g. a pattern of arrangement of prescribed data units), obtained in accordance with the format of the DDS reproducing apparatus, while scanning the magnetic tape. Then, a reference value may be measured for each of the streaming recorded areas distinguished.
However, when scanning a magnetic tape to measure a reference value, the magnetic tape is run at a prescribed speed other than any integral multiple of the regular speed so that scanning can take place in as even a phase position as possible relative to each of the plurality of tracks in a given section of tape running. There is a circumstance that, because the magnetic head appropriately traces the track when scanning for reference value measurement, data contents inherent between streaming recorded areas cannot always be read out appropriately. If, as a result, a data pattern inherent between streaming recorded areas, for instance, cannot be distinguished, a reference value will be measured with the linked plurality of these streaming recorded areas being looked upon as a single streaming recorded area.
Thus, in the stage of scanning a magnetic tape to measure a reference value, it is required to distinguish each streaming recorded area section at as high a level of accuracy as possible.
According to the present invention, there is provided a recording tape medium, whereon data are recorded in prescribed units of data each corresponding to a track formed by a helical scanning system, on which to be further recorded are: first track identifying information for identifying individual tracks; and second track identifying information for identifying, with respect to the tracks each formed for a unit of recording operation, the track on which the pertinent unit of recording operation started.
According to the invention, there is also provided a recording apparatus for recording data in prescribed units of data each corresponding to a track recorded on a recording tape medium by a helical scanning system, equipped it with: first track identifying information generating means for generating first track identifying information for identifying individual tracks; second track identifying information generating means for generating second track identifying information for identifying the track on which a unit of recording operation started in a state wherein the recording tape medium does not stop running on the way; and unit data forming means for forming the units of data so disposed as to insert the first track identifying information and second track identifying information including information regarding the track position to which each unit of data corresponds into the units of data.
According to the invention, there is further provided a measuring apparatus applicable to an apparatus for measuring, when data are reproduced from a track recorded on a recording tape medium by a helical scanning system, a tracking detection period from the time a rotary drum provided with a reproducing head is in a reference phase position in a period of one rotation until the time the head performs reproduction in a prescribed position on the track; generating a servo control signal for a relative speed with respect to the running speed of the tape and the rotating speed of the rotary drum by comparing this measured value of the tracking detection period with a preset reference value; performing tracking control during reproduction on the basis of this servo control signal; and measuring the reference value, wherein, on each track of the recording tape medium are recorded first track identifying information for identifying individual tracks and second track identifying information for identifying the track on which the pertinent unit of recording operation started in a state wherein the recording tape medium does not stop running on the way, the measuring apparatus being provided with tape running control means for causing the recording tape medium to run at a prescribed running speed appropriate for obtaining the reference value; reference value setting means for sampling the measured values of a plurality of the tracking detection periods obtained in a state in which the recording tape medium is run, calculating the tracking detection period in a just tracking phase state on the basis of this plurality of measured values, and setting the result of calculation as the reference value; unit recorded area identifying means for identifying sections of unit recorded areas recorded by the unit recording action on the basis of the first track identifying information and the second track identifying information read out of the recording tape medium in a state wherein the recording tape medium is run; and control means for causing a setting action to be executed by the reference value setting means for each identified unit recorded area.
According to the above-described configuration, the first track identifying information by which tracks can be identified and the second track identifying information by which tracks, each of which is formed for a round of streaming of recording accomplished in a state wherein the recording tape medium does not stop running on the way, are identified are recorded on a tape recording medium on a track-by-track basis, and when, for instance, a reference value for timing ATF servo is to be measured, sections of streaming recorded areas (append points) are identified on the basis of the aforementioned first and second track identifying information. Since, according to this, detection is carried out while monitoring their continuity on the basis of serial numbers assigned to recording tracks, sections of streaming recorded areas can be detected more reliably than when only the pattern of arrangement of frame (track) numbers in recorded unit data formed by a prescribed number of tracks is relied upon.